weight and manuverablity
Tanker was 30,000 to 50,000 fully loaded. Destroyer 8,000 to 9000 tonnes. Destroyers are maneuverable, tankers are not. both should have done avoidance maneuvers, but the most effective and culpable should have been the destroyer. Not only that, the destroyer was bristling with radar/instrumentation, and should have had unimpeachable situational awareness.
Wife thinks with 2 accidents, it was some diddling with gps signals that gave bad info on purpose.